This invention relates to an optical signal repeating and amplifying device and an optical level adjusting device which are applied to the optical WDM transmission.
The optical WDM transmission system that optical signals with different wavelengths are transmitted in the lump through one optical fiber allows a large-capacity optical transmission. In particular, owing to the development of high-gain and high-power optical amplifiers, such as an erbium-doped optical fiber amplifier, a long-distance and large-capacity optical transmission can be realized. In repeating optical signals in the optical transmission, to amplify the optical signals unalteredly without converting into electrical signals can contribute effectively to the miniaturization of repeating station, thereby reducing the cost of transmission. At present, to realize a further long-distance optical transmission by using a multiple-stage optical repeating and amplifying has been expected.
However, conventional optical signal repeating and amplifying device and optical level adjusting device have some problems described below.
First, due to the limitation on output power of optical amplifier, the optical power per one wave is limited when the number of optical signals multiplexed is increased. Thereby the transmission distance is also limited to be short.
Second, with an increase in the number of repeating amplifiers, the difference in optical level between wavelengths due to the gain deviation of optical amplifier is increased and an ASE noise generated from optical amplifier is also increased. Thereby the reception sensitivity must be reduced. Further, in connecting multiple-stage optical amplifiers, the optical level may be greatly different between wavelengths because optical amplifiers have different gains depending on wavelength.
Accordingly, it is an object of the invention to provide an optical signal repeating and amplifying device that the reception sensitivity can be enhanced by removing an ASE noise, the total optical intensity of optical signals to be output after wavelength-multiplexing can be increased, and the level of wavelength lights in WDM optical signal can be equalized.
It is a further object of the invention to provide an optical level adjusting device that the optical level of each wavelength can be adjusted into an arbitrary value.
According to the invention, an optical signal repeating and amplifying device, comprises:
an optical amplifier which amplifies an optical signal to be input thereto and then outputs it; and
an optical filter means through which only one wavelength light of the optical signal to be output from the optical amplifier is passed.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights;
a plurality of optical transmission lines through which the plurality of wavelength lights from the first optical demultiplexer-multiplexer are separately transmitted; and
a second optical demultiplexer-multiplexer which multiplexes the optical signals transmitted through the plurality of optical transmission lines into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately transmitted; and
a plurality of optical reflecting mirrors which reflect separately the demultiplexed plurality of wavelength lights transmitted through the plurality of optical transmission lines to turn them back.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately transmitted; and
an optical dividing and coupling means through which each of the plurality of wavelength lights transmitted through each of the plurality of optical transmission lines is re-input to the optical demultiplexer-multiplexer while by-passing a different one of the optical transmission lines without overlapping with another wavelength light.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights;
a plurality of optical filters through which the plurality of wavelength lights from the first optical demultiplexer-multiplexer are separately passed; and
a second optical demultiplexer-multiplexer which multiplexes the optical signals passed through the plurality of optical filters into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical divider which divides a wavelength-multiplexed optical signal into a plurality of lights;
a plurality of optical filters through which the plurality of wavelength lights from the optical divider are separately passed; and
an optical coupler which couples the optical signals passed through the plurality of optical filters into a wavelength-multiplexed optical signal and outputs it.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical filters through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately passed; and
a plurality of optical reflecting mirror which reflect separately the demultiplexed plurality of wavelength lights passed through the plurality of optical filters to turn them back.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical divider-coupler which divides the wavelength-multiplexed optical signal from the optical circulator into a plurality of lights and couples a plurality of lights into a wavelength-multiplexed optical signal;
a plurality of optical filters through which the divided plurality of lights to be output from the optical divider-coupler are separately passed; and
a plurality of optical reflecting mirrors which reflect separately the divided plurality of lights passed through the plurality of optical filters to turn them back.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical divider-coupler which divides the wavelength-multiplexed optical signal from the optical circulator into a plurality of lights and couples a plurality of lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines which the divided plurality of lights to be output from the optical divider-coupler are separately transmitted;
a plurality of optical filters through which the divided plurality of lights from the plurality of optical transmission lines are separately passed; and
an optical dividing and coupling means through which each of the plurality of lights passed through each of the plurality of optical filters is re-input to the optical divider-coupler while by-passing a different one of the optical transmission lines without overlapping with another light.
According to another aspect of the invention, an optical level adjusting device, comprises:
an optical demultiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights;
a plurality of optical attenuators which attenuate separately the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer; and
an optical multiplexer which multiplexes the attenuated wavelength lights to be output from the plurality of optical attenuators into a wavelength-multiplexed optical signal and output it.
According to another aspect of the invention, an optical level adjusting device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical attenuators which attenuate separately the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer; and
a plurality of optical reflecting mirrors which reflect separately the attenuated plurality of wavelength lights passed through the plurality of optical attenuators to turn them back through the plurality of optical attenuators to the optical demultiplexer-multiplexer.
According to another aspect of the invention, an optical level adjusting device, comprises:
an optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical transmission lines through which the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer-multiplexer are separately transmitted;
an optical dividing and coupling means through which each of the plurality of wavelength lights transmitted through each of the plurality of optical transmission lines is re-input to the optical demultiplexer-multiplexer while by-passing a different one of the optical transmission lines without overlapping with another wavelength light; and
a plurality of optical attenuators which are disposed between any two of the optical transmission lines to attenuate separately the demultiplexed plurality of wavelength lights to be transmitted therebetween.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal to be input thereto into a plurality of different wavelength lights;
a plurality of optical amplifiers which amplify separately the demultiplexed plurality of different wavelength lights; and
a second optical demultiplexer-multiplexer which multiplexes the amplified wavelength lights to be output from the plurality of optical amplifiers into a wavelength-multiplexed optical signal.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of optical amplifiers which amplify separately the demultiplexed plurality of different wavelength lights to be output from the optical demultiplexer-multiplexer; and
a plurality of optical reflecting mirrors which reflect separately the plurality of wavelength lights to be output from the plurality of optical amplifiers to turn them back through the plurality of optical amplifiers to the optical demultiplexer-multiplexer.
According to another aspect of the invention, an optical signal repeating and amplifying device, comprises:
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal to be input thereto into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of first optical transmission lines which are connected with the input-output ports on the demultiplex side of the optical demultiplexer-multiplexer;
a plurality of optical divider-couplers which are connected to the ends of the plurality of first optical transmission lines;
a plurality of second optical transmission lines which connect between different two of the plurality of optical divider-couplers, the connecting not to be in parallel to another connecting; and
a plurality of bi-directional optical amplifiers which are inserted into the plurality of second optical transmission lines and amplify an optical signal to transmit therethrough.
According to another aspect of the invention, an optical level adjusting device, comprises:
a first optical demultiplexer-multiplexer which demultiplexes a wavelength-multiplexed optical signal to be input thereto into a plurality of different wavelength lights;
a plurality of optical amplifiers which amplify separately the demultiplexed plurality of different wavelength lights; and
a second optical demultiplexer-multiplexer which multiplexes the amplified wavelength lights to be output from the plurality of optical amplifiers into a wavelength-multiplexed optical signal; and
means for controlling separately the gain of the plurality of optical amplifiers.
According to another aspect of the invention, an optical level adjusting device, comprises:
an optical circulator through which a wavelength-multiplexed optical signal to be input to the input port is output from the input-output port and a wavelength-multiplexed optical signal to be input to the input-output port is output from the output port;
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal from the optical circulator into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of bidirectional optical amplifiers which amplify separately the demultiplexed plurality of different wavelength lights to be output from the optical demultiplexer-multiplexer;
a plurality of optical reflecting mirrors which reflect separately the plurality of wavelength lights to be output from the plurality of optical amplifiers to turn them back through the so plurality of optical amplifiers to the optical demultiplexer-multiplexer;
means for controlling separately either the gain of the plurality of optical amplifiers or the reflectivity of the plurality of optical reflecting mirrors.
According to another aspect of the invention, an optical level adjusting device, comprises:
an optical demultiplexer-multiplexer which demultiplexes the wavelength-multiplexed optical signal to be input thereto into a plurality of wavelength lights and multiplexes a plurality of wavelength lights into a wavelength-multiplexed optical signal;
a plurality of first optical transmission lines which are connected with the input-output ports on the demultiplex side of the optical demultiplexer-multiplexer;
a plurality of optical divider-couplers which are connected to the ends of the plurality of first optical transmission lines;
a plurality of second optical transmission lines which connect between different two of the plurality of optical divider-couplers, the connecting not to be in parallel to another connecting;
a plurality of bi-directional optical amplifiers which are inserted into the plurality of second optical transmission lines and amplify an optical signal to transmit therethrough; and
means for controlling separately the gain of the plurality of bi-directional optical amplifiers.